Cardiopulmonary blood volumes at rest and during muscular exercise measured by 113mIn radiocardiography.

Cardiac output, stroke volume, right heart and left heart blood volume, pulmonary blood volume and pulmonary mean time were measured at rest and during muscular exercise in 14 healthy subjects in the supine position. The method used was 113mIn radiocardiography measured precordially with a single detector. The results were analyzed with a minicomputer by a modified gamma function fitting method. The increase in cardiac output during exercise was 140 per cent (p is less than 0.001). The stroke volume increased 15 per cent (p is less than 0.05) in subjects with heart rates less than 160 beats/min, and decreased in subjects with heart rates greater than or equal to 160 beats/min. The right heart blood volume decreased from 115 ml/m2 to 105 ml/m2 to 215 ml/m2 (5 per cent; p is less than 0.1) and the left heart blood volume decreased from 120 ml/m2 to 110 ml/m2 (5 per cent; p is less than 0.01). The total heart blood volume thus decreased from 235 ml/m2 (5 per cent; p is less than 0.05). The pulmonary blood volume showed a corresponding increase from 250 ml/m2 to 280 ml/m2 (12 per cent; p is less than 0.005), and the cardiopulmonary blood volume did not markedly change (485 ml/m2 and 495 ml/m2). Pulmonary mean time decreased from 5.0 s to 2.4 s (52 per cent; p is less than 0.001).